This invention relates generally to pressurized fluid handling valves, and more particularly to valves provided to control both the throttling mechanism and inlet valve position for an air compressor depending upon the compressor outlet pressure.
As shown in FIG. 1 of this invention, compressors 12 are now used to power jackhammers, riveters or other items 13 which often only are intermittently used by the operator. The compressor 12 includes a driven fan portion 16, a motor 14, an inlet 15 and an outlet 24. The inflow of air to the driven fan portion 16 is controlled by the position of piston 19 within compressor valve 18 (the piston is shown displaced at 19'). A spring 29 is included to bias the piston 19 in valve 18 to the left as illustrasted in FIGS. 1 and 2, thereby placing the compressor 12 in a loaded state. The speed of the motor 14 is directly controlled by a throttle 20.
When the pressure in conduit 26 of compressor outlet 24 reaches a certain limit, a diaphragm 30 (within regulator valve 10) compresses a spring 32 and permits pressure to flow from conduit 26 to control tube 28. The pressure in control tube 28, as regulated by the valve 10 and a release outlet 22, controls the operation of valve 18 and throttle 20. The outlet 22 of many systems is connected between the compressor valve 18 and the compressor 12, as shown at 22', to reduce the vacuum at compressor inlet 15.
When the compressor 12 is in an unloaded condition due to the workpiece 13 consuming little or no air, the pressure in compressor outlet 24 will rise causing the regulator valve 10 to open. The pressure in the control tube 28 will then increase which will concurrently close the valve 18 and idle the throttle 20, limiting the air pumped by the compressor 12.
If the compressor outlet pressure drops due to the operation of the workpiece 13, the valve 10 will close. The pressure in the control tube 28 will quickly bleed out of the opening 22, thus causing the compressor valve 18 to open and increase the position of the throttle 20 increasing the speed of compressor 16.
In the above system, as much as 900 cubic feet per hour will pass through opening 22 when the compressor 16 is unloaded and the valve 10 is in a fully open position. This continual air passage presents several limitations.
The first limitation is that any pressure which passes through the release opening must be supplied by the compressor. Therefore, excessive compressor operation and wear occurs. Relatedly, icing often occurs when excessive compressed air containing moisture rapidly travels through the regulator valve 10 and opening 22.
The first solution to the icing problem is to insert heating elements to the areas prone to icing. These heating elements however are expensive and icing often occurs at other unexpected locations. The second icing solution involves chemically treating the air which is about to enter valve 10 with a deicing agent. Besides requiring expensive equipment to insert the agent, it is also necessary for someone to monitor the level of the agent in the reservoir. The deicing agents often are abrasive on whatever components they encounter. The final solution to this problem is to provide water moisture removal equipment upstream of the pressure valve 10. This equipment is expensive and bulky.
Another limitation with the above compressor control system involves the loud noise produced by air escaping from the release opening. Dirt and impurities in the air block or change the shape of the opening, eventually affecting the downstream pressure of the compressor as well as interrelated throttling operation of the compressor.
To deaden the excessive opening noise, a muffler is often inserted over the opening 22. Besides making the device more complex and expensive, the muffler often becomes clogged or breaks.
The foregoing illustrates limitations known to exist in present devices. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.